Communication networks include wired and wireless networks. Example wired networks include the Public Switched Telephone Network (PSTN) and the Internet. Example wireless networks include cellular networks as well as unlicensed wireless networks that connect to wire networks. Calls and other communications may be connected across wired and wireless networks.
Cellular networks are radio networks made up of a number of radio cells, or cells, that are each served by a base station or other fixed transceiver. The cells are used to cover different areas in order to provide radio coverage over a wide area. When a cell phone moves from place to place, it is handed off from cell to cell to maintain a connection. The handoff mechanism differs depending on the type of cellular network. Example cellular networks include Universal Mobile Telecommunications System (UMTS), Wide-band Code Division Multiple Access (WCDMA), and CDMA2000. Cellular networks communicate in a radio frequency band licensed and controlled by the government.